For the past seven years, engineers at the SLAC National Linear Accelerator Laboratory in California have been grappling with the process of assembling and assembling the world’s largest camera for the LSST telescope, which is currently under construction at the Vera C. Rubin Observatory. If all goes according to plan, in May 2023 this camera will travel to a desert region in northern Chile to be installed on a telescope, after which verification, alignment and commissioning will begin.

Building a camera of this scale and complexity takes a lot of time, effort and patience. “But we finally got to the point where all the components and mechanisms of the camera were assembled,” says Hannah Pollek, the project’s chief engineer.

Any camera needs lenses, and the LSST telescope camera is no exception. Its 1.57 meter diameter lens is the largest in the world and entered the Guinness Book of Records. As part of the telescope, this lens will capture light reflected from three separate mirrors and focus it on the surface of the photosensitive matrix.

The optical system of the LSST telescope will allow it to “cover up” a region of the sky with a magnitude of 3.5 angular degrees, about seven times the full moon. The camera will take a series of photos, each lasting 15 seconds, and then the telescope will move to the next part of the sky. And so he will study the night sky for many years.

Photosensitive CCD sensors are placed behind the lenses, their position is clearly visible in the second picture, and the different colors of the individual areas are the result of these sensors being produced by different manufacturers. However, regardless of the difference in color, all elements have the same characteristics and will all be able to synthesize images with a resolution of 3.2 gigapixels.

Cooling down to -100 degrees Celsius is required for the normal operation of CCD sensors and the elimination of their thermal noise. This cooling is carried out by a cryostat device and a pipeline system where coolant is fed to the sensors.

However, the CCD sensors are not the only parts of the camera that require intense cooling. The electronics just behind the sensors emit about 1.1 kW of heat, which is a big problem. Fortunately, there is no need for cooling to cryogenic temperatures, but the liquid cooling system is also a huge headache for engineers. Recently they had to change the type of coolant which resulted in a complete redesign of the piping system and it continues to this day. One of the few components installed in the camera are optical filters made of pure optics. sputtered glass that only lets in light from certain wavelengths. Some of these filters are made in Massachusetts and some in Provence, France, and are already waiting to be installed in the cleanroom.

Five of these light filters will be in the slots of the carousel-type driver, and the sixth will be in a special slot where it can be replaced with any filter in the carousel. The process of replacing the light filter and adjusting the lenses and sensors accordingly takes about 2 minutes. This whole system is ready and has been tested using cavities made of thin metal that weigh the same as glass light filters.

After installing the light filters, engineers will point the camera at the ground and test its performance in dark conditions by moving around a light source of different brightness.

After preliminary testing, lenses, light filters and other glass components will be removed and placed in special shipping packaging. The camera itself will be installed in a special container with elements that hold it, designed to dampen vibration and oscillations with acceleration up to 2 g. And finally, this container will be loaded onto a Boeing 747 carrier that will deliver its cargo by direct flight from San Francisco to Santiago. Source